1. Field of the Invention
The present invention relates to a light-emitting device and a lighting device each having a self-recovery function.
2. Description of the Related Art
In recent years, research and development have been extensively conducted on a light-emitting element using electroluminescence (EL). In a basic structure of such a light-emitting element, a layer containing a light-emitting substance (an EL layer) is interposed between a pair of electrodes. By voltage application to this element, light emission can be obtained from the light-emitting substance.
Since such a light-emitting element is of self-light-emitting type, it is considered that the light-emitting element has advantages over a liquid crystal display in that visibility of pixels is high, backlight is not required, and so on and is therefore suitable for a flat panel display element. Besides, such a light-emitting element has advantages in that it can be formed to be thin and lightweight, and has very high response speed.
Furthermore, since such a light-emitting element can be formed into a film shape, surface light emission can be easily obtained. Therefore, a large-area element using surface light emission can be formed. This is a feature which is difficult to obtain in point light sources typified by an incandescent lamp and an LED or linear light sources typified by a fluorescent lamp. Accordingly, a light-emitting element is extremely effective for use as a surface light source applicable to lighting and the like.
In order to manufacture a light-emitting element, the following process is generally employed, for example: after one of electrodes is formed, an EL layer is formed over the electrode, and the other of the electrodes is formed over the EL layer.
In the process in which the light-emitting element is manufactured as described above, an impurity may enter the light-emitting element for some reason. Such an impurity causes a defect in the electrode or the EL layer to adversely affect light emission of the light-emitting element. Even when a defect is not caused in the electrode or the EL layer, current flows in a concentrated manner in a region where the impurity exits in application of voltage to the light-emitting element and the region is locally heated to a high temperature; in such a case, a defect may be caused in the EL layer.
When a defect is caused in the EL layer of the light-emitting element, the possibility of occurrence of a short circuit between the pair of electrodes is increased; in the case where the short circuit is caused, the element cannot function as a light-emitting element.
As an example of a technique for preventing a short circuit between a pair of electrodes, a technique in which a defect in an EL layer is filled with an insulating material to prevent a short circuit between a pair of electrodes is given (e.g., see Patent Document 1).